body {
    margin: 0;
    height: 100vh;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

header, footer {
    transition: background 1s linear, color 1s linear;
    padding: 0.5em 1em;
    font-size: clamp(0.8em, 3vw, 1.2em);
}

.top-bar {
    text-align: center;
    margin-top: 1em;
}

.back-btn {
    background: rgba(255, 255, 255, 0.2);
    border: 1px solid white;
    color: white;
    font-weight: bold;
    transition: background 0.5s, color 0.5s;
}

.back-btn:hover {
    background: rgba(255, 255, 255, 0.5);
    color: black;
}

.sentence {
    position: absolute;
    font-size: clamp(0.9em, 5vw, 2em); /* 自适应移动端字体大小 */
    font-weight: bold;
    text-shadow: 0 0 8px rgba(0, 0, 0, 0.8);
    opacity: 0;
    transition: opacity 2s ease, color 1s linear;
    white-space: nowrap;
    z-index: 10;
    pointer-events: none;
}

section {
    flex: 1;
    position: relative;
}
/* 星星样式 */
.star {
    position: absolute;
    width: 2px;
    height: 2px;
    background: white;
    border-radius: 50%;
    opacity: 0.8;
    pointer-events: none;
    animation: twinkle 2s infinite;
}

@keyframes twinkle {
    0%, 100% { opacity: 0.8; }
    50% { opacity: 0.2; }
}

/* 毛玻璃文字效果 */
.glass {
    color: white;
    text-shadow: 0 0 8px rgba(0,0,0,0.8);
    backdrop-filter: blur(2px);
}

.italic { font-style: italic; }
.shadow { text-shadow: 2px 2px 6px rgba(0,0,0,0.7); }